Effects of Cannabis Abstinence on Symptoms and Cognition in Depression

Effects of Extended Cannabis Abstinence on Symptoms and Cognition in Depressed Individuals

The objective of this study is to assess the changes in symptoms and cognition that occur after a 28-day abstinence period in patients with comorbid Cannabis Use Disorder (CUD) and Major Depression (MDD). This study employs a 28-day abstinence paradigm a total of 8 visits to the CAMH Russell site (screening, training, baseline, week 1, week 2, week 3, week 4, follow-up). Participants should be between the ages of 18-55, meet criteria for moderate depression and CUD, be non-treatment seeking, and be on a stable dose of antidepressant medication. The study visits will take up a total of approximately 22.5 hours with compensation for time provided. These visits will involve multiple clinical, substance use, and cognitive assessments. Abstinence will be maintained by weekly behavioural coaching sessions and contingency reinforcement.

Inclusion Criteria:

• ages 18-55
• meet DSM-5 diagnostic criteria for cannabis use disorder (cannabis use >1 g/day, CUDIT score >12)
• meet DSM-5 diagnostic criteria for Major Depressive Disorder as determined using the SCID
• be an outpatient receiving a stable dose of antidepressant medication(s) for at least 1 month
• have a Hamilton Depression Rating Scale (HDRS-17) baseline total score greater than 14
• have a Full Scale IQ greater than 80 as determined by the WTAR
• be a non-treatment seeking cannabis user
• evidence of sufficient motivation and effort as measure by a Test of Memory Malingering (TOMM) score greater than 45
• urinary baseline THC-COOH levels greater than 150 ng/ml

Exclusion Criteria:

• meets criteria for abuse or dependence of alcohol or other illicit substances within the part 6 months (with the exception of cannabis, nicotine, or caffeine)
• positive urine screen for illicit substances other than cannabis, nicotine or caffeine
• current suicidal or homicidal ideation
• psychotic disorder diagnosis (e.g. schizoaffective disorder, major depression with psychotic features) as determined by the SCID
• head injury with loss of consciousness greater than 2 minutes or requiring hospitalization
• neurological or medical condition determined to effect cognition
• be treatment seeking for cannabis use